<h3>Step 1</h3>
<p>Drag the thumbtack so that it appears to lie flush against the surface in an
image.  The surface is outlined with a red shape.  When you are done, the red
thumbtack pin should appear to face away from the surface.</p>

<p>We suggest aligning the two black lines so they are parallel with other
lines in the photograph.  Drag with the right mouse button to rotate the black
lines.  This will make step 2 easier.</p>

<h3>Step 2</h3>
<p>On the right, you will see a distorted version of the shape.  This is what
the shape looks like if you are viewing it from a top-down view.  If the
thumbtack is correct, then this distorted shape should appear to face forward.</p>

<p>To adjust the shape on the right, you can drag it with the mouse.  Please
also rotate it with the <i>right mouse button</i> so that it is upright.</p>

<p>Please rotate the shape by dragging with the right mouse button so that any
patterns in the shape are aligned vertically.  Adjusting the orientation should
also become easier when the shape is aligned.</p>

<p>For example, if there is a tile pattern in the shape, the tiles should be
parallel in the right image.  If it is a square in the scene, it should appear
as a square in the right image.  The outline of the shape on the right is not
important; the texture and patterns inside is what matters.</p>

<h3>Adjusting the result</h3>

<p>If dragging moves the shape too fast, click the &quot;Fine adjustment&quot;
button.  You may also zoom with the &quot;Zoom in&quot; button.</b>


<br/>
<h2>Good Examples</h2>

<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_good4.jpg"/>
			<p class="caption">On the left, the thumbtack lies flush agains the
			floor.  On the right, the tile patterns are aligned in straight lines.</p>
		</div>
	</div>
</div>
<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_good7.jpg"/>
			<p class="caption">On the left, the thumbtack lies flush agains the
			table.  On the right, the wood patterns are aligned in a straight
			line.</p>
		</div>
	</div>
</div>
<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_good2.jpg"/>
			<p class="caption">Some surfaces will not have a repeating texture.
			Do your best to align it so that the thumbtack faces away from the
			surface and the right shape faces forward.</p>
		</div>
	</div>
</div>
<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_good6.jpg"/>
			<p class="caption">In some scenes, the thumbtack may no longer look
			correct once you get the right side aligned properly.  This is
			fine; it is more important that the shape on the right looks good.
			Patterns inside the shape should appear parallel and not
			slanted.</p>
		</div>
	</div>
</div>
<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_good8.jpg"/>
			<p class="caption">The frame has 90 degree angles and faces forward.</p>
		</div>
	</div>
</div>

<br/>
<h2>Bad Examples</h2>
<p>We will reject HITs that do not follow these instructions.  We would love
to approve everyone, but then some people take advantage of our HIT.  We have
no choice but to reject bad submissions.</p>

<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_bad1.jpg"/>
			<p class="caption">The thumbtack is not facing the right direction.</p>
		</div>
	</div>
</div>

<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_bad2.jpg"/>
			<p class="caption">The thumbtack looks okay, but the right side
			does not.  You should drag the right image until it looks parallel.
			See below for the correct version.</p>
		</div>
	</div>
</div>

<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_bad3.jpg"/>
			<p class="caption">Both sides look okay, but the right side is not
			rotated properly.  Drag with the right mouse button to fix it.  See
			below for the correct version.</p>
		</div>
	</div>
</div>

<h2>Good Examples</h2>
<p>This is what the &quot;bad examples&quot; should have done:</p>

<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_good1.jpg"/>
			<p class="caption">This is the correct version of the above.</p>
		</div>
	</div>
</div>

<div class="row">
	<div class="span12">
		<div class="thumbnail">
			<img src="{{ STATIC_URL }}img/mturk/rectify_material_good5.jpg"/>
			<p class="caption">This is the correct version of the above.</p>
		</div>
	</div>
</div>

<br/>
<h2>Why are we doing this?</h2>

<p>We are trying to understand the 3D structure of photographs.  These
thumbtack orientations allow us to <i>rectify</i> shapes so that they appear to
face the camera. This experiment is part of ongoing research at Cornell University.  Thanks
for participating!</p>
